What Is Grade A Mulch?

Choosing a premium mulch benefits your soil and feeds your plants.

Mulch is shredded wood used as a protective covering for landscaping. Mulch maintains moisture for plants, provides nutrients to soil and adds aesthetic value to yards. Using mulch mixed with compost, if not carefully chosen, or other materials may wreak havoc on your garden with volunteer seedlings (poison ivy, anyone?) or toxins that leach into the soil. Grade A mulch is aged, free of contaminants and contains only tree bark.

Aging

Decomposing mulch contributes nutrients to the soil more efficiently than newer bark. Healthy plants depend on a 30-to-1 ratio of carbon to nitrogen within the soil. Wood, a carbon-based material, hungrily bonds with nitrogen in the soil for speedier decomposition; so the newer the mulch, the more it will deplete nitrogen. The less nitrogen in soil, the longer the mulch takes to break down, potentially burning your plants. Mulch that has been aged for a few years, however, extracts from the soil less nitrogen, because it has already begun to break down. Aged mulch is particularly beneficial for newer plantings that require a lot of nitrogen.

Blending

A mulch "blend" may denote a mixture of bark from various tree species or it may refer to mixing the wood with compost. Compost is OK, but ask your professional landscaper or garden center about the type of matter used in the blending process. More often than not, the compost consists of an unknown mix of organic and inorganic materials. You'll encounter enough mystery with the season's weather predictions, so choose a mulch blend you can trust.

Dyeing

Dyeing wood mulch is one way for manufacturers to camouflage impurities. Some red-dyed mulch is wood procured from demolished construction projects. Such wood is often chemically treated and therefore toxic to soil. A particularly egregious wood preservative known as chromium copper arsenate can devastate soil by killing important soil bacteria, microorganisms and worms, and is most often found in lesser-grade mulch.

Shredding

Single, double or triple shredding refers to the number of times the bark was passed through the grinder. The smaller the grind, the quicker the decomposition process. It is important to note that the type of machine used during the shredding process determines the size and uniformity of the mulch. However, shredding has little to do with mulch grade.

About the Author

Vanessa LaFaso Stolarski has 14 years experience in publishing and 17 years in the restaurant industry. She has served as food and wine editor for a Washington, D.C.-area newspaper company, and managing editor for "Northern Virginia" magazine. As founder of The Locavore Project-WV, she works with sustainable farms to promote consumer awareness and whole-food nutrition.